• Energy Research

Abstract Poland is the EU’s largest producer of cherry, which largely is further processed. As a consequence, a problematic waste – cherry pomace – is generated as by-product. Among the new sustainable technologies for organic waste valorization particularly perspective are thermochemical methods, which can be divided into conventional one, i.e., dry route (e.g. pyrolysis, gasification) and wet route (i.e. hydrothermal treatment). Herein, we proposed a two-stage thermochemical processing route for the conversion of cherry pomace, i.e., hydrothermal treatment followed by CO2 gasification. Firstly, we transformed the feedstock into biochar via hydrothermal processing. The aim of this stage was to analyze the effect of processing temperature (200–350 °C) on the distribution of the yield of various groups of products. The residual biochar was obtained with the highest yield (33–57 wt%). Among the gas-phase products, the dominant constituent was CO2. The upgrading of the biochars through gasification with CO2 to ensure the sustainability of conversion was the subsequent step. The quality of the biochars was examined by infrared spectroscopy, proximate and ultimate analysis, SEM, and low-temperature nitrogen adsorption. The activation energy ranged between 668 and 732 kJ mol−1 for the gasification of the biochar prepared at 275 and 200 °C, respectively. It was found that biochars produced at different conditions exhibit various properties as a result of gradual degradation of the original components of the raw material and increase in aromaticity occurring with the increase in the processing temperature.

Hydrothermal liquefaction of biomass in near-/supercritical water has attracted great attention in recent years. Although this technology seems to be promising for transformation of microalgal biomass, the information on the impact of feedstock and processing variables of continuous hydrothermal liquefaction on the properties of bio-oil provided in previous literature is scarce. Herein, the low-lipid Scenedesmus sp. biomass has been transformed to bio-oils through continuous hydrothermal liquefaction under various process conditions. The influence of temperature and residence time on bio-oil characteristic was discussed based on characterization by FT-IR, GC–MS and gel permeation chromatography. The relative degree of branching of carbon chain of bio-oils components was estimated based on the deconvolution of methyl and methylene FT-IR absorption bands. The presumptive pathways of the reactions have been postulated. Finally, it was found that the parameters of bio-oil may be tailored by adjustment of processing variables, however, possible subsequent/parallel effects must be considered while designing the process.

Wet organic wastes are especially troublesome in valorization. Therefore, innovative solutions are still in demand to make valorization feasible. In this study, we tested a new transformation route of a blackcurrant pomace as a high-moisture industrial waste through a series of high-temperature and pressure solvothermal liquefaction experiments. The feedstock was directly converted under near-critical conditions of the binary solvent system (water/2-propanol). The goal was to examine the effect of conversion parameters (temperature, biomass-to-solvent ratio) on the change in the yield of resultant bioproducts, as well as the quality thereof. The experiments were conducted in a batch autoclave at a temperature between 250 and 300 °C. The main product of the transformation was liquid biocrude, which was obtained with the highest yield (ca. 52 wt.%) at 275 °C. The quality of biocrude was examined by ATR-FTIR, GC-MS, and elemental analysis. The ultimate biocrude was a viscous heterogeneous mixture containing various groups of components and exhibiting evident energy densification (ca. 145–153%) compared to the value of the feedstock. The proposed processing method is suitable for further development toward efficient valorization technology. More specifically, the co-solvent additive for liquefaction is beneficial not only for the enhancement of the yield of the desired product, i.e., biocrude, but also in terms of technological aspects (reduction of operational pressure and temperature).

Abstract Lignin stands the most abundantly available source of renewable aromatic compounds which is generated as a useless waste by-product in numerous industrial processes, e.g., in pulp and paper manufacturing as well as during second-generation ethanol production. The present work aims to investigate the effect of reaction conditions (particularly the reaction atmosphere type) on the composition of the volatiles that evolved during the pyrolysis of lignin. The pyrolytic studies were carried out using coupled microscale techniques, i.e., Py-GC-MS, and Py-FT-IR. The pyrolysis is usually carried out under an inert atmosphere. Herein, there was additionally studied comprehensively the effect of oxidizing (CO2 and air) and reducing atmosphere (H2). There was found a profound impact of the processing temperature on the composition changes of volatiles. A minor effect was noted for the pyrolysis atmosphere on the qualitative composition of the volatiles, but certain quantitative differences between their concentration were observed. Their composition confirmed the complex molecular structure of lignin. Among the identified compounds, there were found phenol derivatives as primary products of cleavage of lignin structures as well as aliphatic oxygen compounds and aromatic hydrocarbons as the products of the secondary decomposition and deoxygenation thereof.

Herein, we proposed new two-stage processing of blackcurrant pomace toward a value-added, hydrocarbon-rich biocrude fraction. The approach consisted of thermochemical liquefaction of a wet-type organic matter into liquid biocrude followed by its upgrade by thermal and catalytic pyrolysis. Particularly, we put effort into investigating the effect of selected catalysts (ZSM-5 and HY zeolite) on the composition of the volatiles released during the pyrolysis of the biocrude. The latter was obtained through liquefaction of the raw material in the binary solvent system of water and isopropanol. The biocrude yield accounted for ca. 45 wt.% of the initial dry biomass. It was a complex mixture of various component groups with an abundant share of oxygenates, especially carboxylic acids and esters. Thereafter, the biocrude was subjected to a pyrolysis study performed by means of the microscale coupled pyrolysis-gas chromatography-mass spectrometry technique (Py-GC-MS). The dominant components identified in the catalytic pyrolytic volatiles were unsaturated hydrocarbons (both cyclic and aliphatic ones) and, to a lesser extent, oxygen and nitrogen compounds. The addition of the ZSM-5 and HY zeolite allowed us to attain the relative total share of hydrocarbons in the volatile fraction equal to 66% and 73%, respectively (in relation to identified compounds). Thus, catalytic pyrolysis over zeolites seems to be particularly prospective due to the promotion of the deoxygenation reactions, which manifested in the noticeable decrease in the share of oxygen compounds in the evolved volatiles. The developed innovative two-stage processing of blackcurrant pomaces allows for obtaining value-added products that could serve as chemicals, biocomponents, and self-contained biofuels as well as bioplastic precursors. The presented contribution brings some new insights into the field of valorization of residuals generated by the food industry sector.

Abstract Poland belongs to the most meaningful producers of fresh food products in the European Union, e.g., apples, cherries, carrots, as well as currants. A significant part of these products are subjected to further processing, which results in the generation of an abundant amount of wet residues, such as pomace. The present paper aims to investigate the possibility of co-processing various industrial residues in the form of fruit pomaces through thermochemical liquefaction toward high-energy-density biocrude and biochar. More specifically, industrial wastes received from commercial juice production, i.e., blackcurrant, apple, and cherry pomaces, were converted under subcritical conditions of the water-isopropyl alcohol solvent system at fixed conditions. Particular focus was put on testing binary and ternary mixture feedstock systems and the possibility of predicting the bioproduct yield. Furthermore, the quality of the resultant biocrudes was analyzed by means of FTIR, GC-MS, and elemental analysis. For all separately studied raw materials and their binary and ternary mixtures, the dominant group fraction was biocrude with its yield ranging between 45.8 and 54.5 wt%. Produced liquids exhibit high energy density (HHV between 30.1 and 32.4 MJ/kg); thus, all of them pose perspective alternative fuels for generating heat and electricity. Also, the solid biochars presented a high energy density (HHV around 24–26 MJ/kg) and can be considered as an alternative energy carrier. The postulated approach aims to increase the flexibility and profitability of future technology of processing useless waste toward value-added bioproducts for the chemical and energy sectors.

One of the most efficient among the methods of managing waste tire rubber is the pyrolysis process which allows for obtaining pyrolysis oil. The as-received, raw tire pyrolysis oil (rTPO) is a comp...